The White-collared Kite (Leptodon forbesi Swann, 1922), previously known by the holotype and three specimens from northeastern Brazil from the late 1980s, is considered by many as a juvenile variant of the Grey-headed Kite (L. cayanensis Latham, 1790). We present new morphological evidence from museum specimens of both species, including a previously misidentified specimen of L. forbesi, and field study to support the validity of the White-collared Kite as a species, now seen as endemic and severely threatened in northeastern Brazil. This species occurs only in remnants of the Atlantic Forest in the states of Alagoas and Pernambuco. It is distinguished from its congener by its white hind-collar, underwing coverts, and leading edge of the wings. The under surface of the secondaries show reduced black barring. The number of white and black tail bands is variable, and not a good diagnostic character. We also review all taxa described for L. cayanensis and show the described subspecies are not valid.